This work presents new experimental results on the kinetics of mineral dissolution in near-critical and supercritical water in a temperature range (T) from 25 to 400°C and a constant pressure of 23 MPa. Kinetic e...This work presents new experimental results on the kinetics of mineral dissolution in near-critical and supercritical water in a temperature range (T) from 25 to 400°C and a constant pressure of 23 MPa. Kinetic experiments were carried out by using a flow reactor (packed bed reactor) of an open system. The dissolution rates of albite and magnetite were measured under these experimental conditions. Na, Al and Si release rates for albite dissolution in water were measured as a function of the temperature and flow velocity in the reaction system. The maximum release rates of Na, Al and Si of albite dissolution in the hydrothermal flow systems under different flow velocities were always obtained at 300°C, that is to say, the maximum albite dissolution rates in the flow systems, regardless of different flow rates, were repeatedly measured at 300°C. Results indicate a wide fluctuation in albite dissolution rates occurring close to the critical point of water. The dissolution rates increased when the temperatures increased from 25 to 300°C and decreased when the temperatures increase from 300 to 400°C. At some flow velocities, the dissolution rates rose as the temperature surpassed 374°C. Albite dissolution was incongruent in water at most temperatures. It was only at 300°C that albite dissolution was congruent. The albite dissolution from 25 to 300°C (at 23 MPa) will change from incongruent to congruent, whereas from subcritical 300 to 400°C (at 23 MPa), the dissolution will change from congruent to incongruent. The release ratio of Al/Si (or Na/Si) is positive at T<300°C, and it is negative at T>300°C. The dissolution rates of magnetite in water increased with increasing T until T at the critical point of water or around it. The authors believe that this is caused by the wide fluctuations in water properties under the conditions from the near-critical to supercritical state.展开更多
The hydrothermal synthesis of single-crystallineβ-MnO2 nanorods and their chemical conversion into single-crystalline LiMn2O4 nanorods by a simple solid-state reaction were reported.This method has the advantages of ...The hydrothermal synthesis of single-crystallineβ-MnO2 nanorods and their chemical conversion into single-crystalline LiMn2O4 nanorods by a simple solid-state reaction were reported.This method has the advantages of producing pure,single-phase and crystalline nanorods.The LiMn2O4 nanorods have an diameter of about 300 nm.The discharge capacity and cyclic performance of the batteries were investigated.The LiMn2O4 nanorods show better cyclic performance with a capacity retention ratio of 86.2% after 100 cycles.Battery cyclic studies reveal that the prepared LiMn2O4 nanorods have high capacity with a first discharge capacity of 128.7 mA·h/g.展开更多
Nanocrystals of Ce1-xMnxO2-δ（x=0.00,0.05,0.10,0.15,and 0.20） were synthesized by a hydrothermal reaction route.The solid solutions crystallized in a cubic fluorite structure with a particle size in the range of 11...Nanocrystals of Ce1-xMnxO2-δ（x=0.00,0.05,0.10,0.15,and 0.20） were synthesized by a hydrothermal reaction route.The solid solutions crystallized in a cubic fluorite structure with a particle size in the range of 11～15 nm.The incorporation of Mn ions in CeO2 resulted in a lattice volume reduction.Mn ions showed a mixed valence state of ＋2,＋3 and ＋4 in CeO2 lattice.An obvious red-shift of the absorption threshold edge was observed from the UV-visible spectrum.Compared with the bulk CeO2,Ce1-xMnxO2-δ nanocrystals exhibited a lower releasing oxygen temperature as indicated by TPR technique.展开更多
Sb^(3+)-doped YBO3 crystals were prepared through a low-temperature hydrothermal method and a high-temperature solid-state technique,respectively.The effects of preparation methods on the morphologies and luminescent ...Sb^(3+)-doped YBO3 crystals were prepared through a low-temperature hydrothermal method and a high-temperature solid-state technique,respectively.The effects of preparation methods on the morphologies and luminescent properties of YBO_(3) phosphors were investi-gated.The YBO3 crystals from the hydrothermal system look likeflowers,whereas those from the solid-state process look like some agglomerates of little spheres.The Sb^(3+)-doped YBO3 powders prepared via both methods showed the blue emission with the peak at around 452 nm,which corresponds to the 3P1→1S0 transition of Sb^(3+)ions.However,the emission intensity of the Sb^(3+)-doped YBO3 from the hydrothermal system is about 3.5 times as much as that from the solid-state process.The(Sb^(3+),Eu^(3+))co-doped YBO3 crystals were also prepared through the two methods.The results showed that the emission intensity of Sb^(3+)ions in(Sb^(3+),Eu^(3+))co-doped YBO3 synthesized by the hydrothermal method is stronger than that by the solid-state process.展开更多
In the polyoxyethylene(PEO)-based solid-state electrolytes,the low ionic conductivity of lithium ions limits its application in solid-state lithium batteries,so optimizing the conduction path of lithium ions is benefi...In the polyoxyethylene(PEO)-based solid-state electrolytes,the low ionic conductivity of lithium ions limits its application in solid-state lithium batteries,so optimizing the conduction path of lithium ions is beneficial to improve the ionic conductivity.In this work,we report the use of hydrothermal carbon nano-sphere(HCS)modified glass fibers(GF)as a functional filler(GF@HCS)to improve the ionic conductivity of PEO composite solidstate electrolytes.The oxygen atoms in the hydroxyl groups on the surface of HCS can be complexed with Li ions as its transport sites,which means that it can promote the longdistance transport of Li ions along the glass fiber surface.With addition of 2 wt%GF@HCS fillers,the degree of crystallinity of PEO composite solid-state electrolyte is the smallest,and the ionic conductivity is significantly increased from 8.9×10^(-5) to 4.4×10^(-4) S·cm^(-1) at 60℃.Moreover,the PEO composite solid-state electrolyte exhibits better lithium-metal interface stability in symmetric lithium batteries and superior rate performance in LiFePO4 solid-state batteries.展开更多
基金We would like to thank the Ministry of Science and Technology and the Ministry of Land and Resources for supporting our projectThe experimental results presented in this paper were obtained with the financial support of GTB basic research fund 9501115+1 种基金the“Climbing Project”95-Pre-39,G1999043212National Natural ScienceFoundation of China grant 29673008.
文摘This work presents new experimental results on the kinetics of mineral dissolution in near-critical and supercritical water in a temperature range (T) from 25 to 400°C and a constant pressure of 23 MPa. Kinetic experiments were carried out by using a flow reactor (packed bed reactor) of an open system. The dissolution rates of albite and magnetite were measured under these experimental conditions. Na, Al and Si release rates for albite dissolution in water were measured as a function of the temperature and flow velocity in the reaction system. The maximum release rates of Na, Al and Si of albite dissolution in the hydrothermal flow systems under different flow velocities were always obtained at 300°C, that is to say, the maximum albite dissolution rates in the flow systems, regardless of different flow rates, were repeatedly measured at 300°C. Results indicate a wide fluctuation in albite dissolution rates occurring close to the critical point of water. The dissolution rates increased when the temperatures increased from 25 to 300°C and decreased when the temperatures increase from 300 to 400°C. At some flow velocities, the dissolution rates rose as the temperature surpassed 374°C. Albite dissolution was incongruent in water at most temperatures. It was only at 300°C that albite dissolution was congruent. The albite dissolution from 25 to 300°C (at 23 MPa) will change from incongruent to congruent, whereas from subcritical 300 to 400°C (at 23 MPa), the dissolution will change from congruent to incongruent. The release ratio of Al/Si (or Na/Si) is positive at T<300°C, and it is negative at T>300°C. The dissolution rates of magnetite in water increased with increasing T until T at the critical point of water or around it. The authors believe that this is caused by the wide fluctuations in water properties under the conditions from the near-critical to supercritical state.
基金Project(2008AA031205)supported by the National High-tech Research and Development Program of China
文摘The hydrothermal synthesis of single-crystallineβ-MnO2 nanorods and their chemical conversion into single-crystalline LiMn2O4 nanorods by a simple solid-state reaction were reported.This method has the advantages of producing pure,single-phase and crystalline nanorods.The LiMn2O4 nanorods have an diameter of about 300 nm.The discharge capacity and cyclic performance of the batteries were investigated.The LiMn2O4 nanorods show better cyclic performance with a capacity retention ratio of 86.2% after 100 cycles.Battery cyclic studies reveal that the prepared LiMn2O4 nanorods have high capacity with a first discharge capacity of 128.7 mA·h/g.
基金Supported by NNSFC (Nos 20671092, 20773132, 20771101)National Basic Research Program of China (No 2007BAE08B01, 2009 CB613306)
文摘Nanocrystals of Ce1-xMnxO2-δ（x=0.00,0.05,0.10,0.15,and 0.20） were synthesized by a hydrothermal reaction route.The solid solutions crystallized in a cubic fluorite structure with a particle size in the range of 11～15 nm.The incorporation of Mn ions in CeO2 resulted in a lattice volume reduction.Mn ions showed a mixed valence state of ＋2,＋3 and ＋4 in CeO2 lattice.An obvious red-shift of the absorption threshold edge was observed from the UV-visible spectrum.Compared with the bulk CeO2,Ce1-xMnxO2-δ nanocrystals exhibited a lower releasing oxygen temperature as indicated by TPR technique.
基金the financial sponsored by the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry and the Encouragement Fund of Young and Middle-aged Scientist of Shandong Province(2006BS04014).
文摘Sb^(3+)-doped YBO3 crystals were prepared through a low-temperature hydrothermal method and a high-temperature solid-state technique,respectively.The effects of preparation methods on the morphologies and luminescent properties of YBO_(3) phosphors were investi-gated.The YBO3 crystals from the hydrothermal system look likeflowers,whereas those from the solid-state process look like some agglomerates of little spheres.The Sb^(3+)-doped YBO3 powders prepared via both methods showed the blue emission with the peak at around 452 nm,which corresponds to the 3P1→1S0 transition of Sb^(3+)ions.However,the emission intensity of the Sb^(3+)-doped YBO3 from the hydrothermal system is about 3.5 times as much as that from the solid-state process.The(Sb^(3+),Eu^(3+))co-doped YBO3 crystals were also prepared through the two methods.The results showed that the emission intensity of Sb^(3+)ions in(Sb^(3+),Eu^(3+))co-doped YBO3 synthesized by the hydrothermal method is stronger than that by the solid-state process.
基金financially supported by the National Natural Science Foundation of China(Nos.21875195,22021001 and 52172184)。
文摘In the polyoxyethylene(PEO)-based solid-state electrolytes,the low ionic conductivity of lithium ions limits its application in solid-state lithium batteries,so optimizing the conduction path of lithium ions is beneficial to improve the ionic conductivity.In this work,we report the use of hydrothermal carbon nano-sphere(HCS)modified glass fibers(GF)as a functional filler(GF@HCS)to improve the ionic conductivity of PEO composite solidstate electrolytes.The oxygen atoms in the hydroxyl groups on the surface of HCS can be complexed with Li ions as its transport sites,which means that it can promote the longdistance transport of Li ions along the glass fiber surface.With addition of 2 wt%GF@HCS fillers,the degree of crystallinity of PEO composite solid-state electrolyte is the smallest,and the ionic conductivity is significantly increased from 8.9×10^(-5) to 4.4×10^(-4) S·cm^(-1) at 60℃.Moreover,the PEO composite solid-state electrolyte exhibits better lithium-metal interface stability in symmetric lithium batteries and superior rate performance in LiFePO4 solid-state batteries.
